Redatuming through a salt canopy and target-oriented salt-flank imaging

Abstract

We describe a new shortcut strategy for imaging the sediments and salt edge around a salt flank through an overburden salt canopy. We tested its performance and capabilities on 2D synthetic acoustic seismic data from a Gulf of Mexico style model. We first redatumed surface shots, using seismic interferometry, from a walkaway vertical seismic profile survey as if the source and receiver pairs had been located in the borehole at the positions of the receivers. This process creates effective downhole shot gathers by completely moving surface shots through the salt canopy, without any knowledge of overburden velocity structure. After redatuming, we can apply multiple passes of prestack migration from the reference datum of the bore-hole. In our example, first-pass migration, using only a simple vertical velocity gradient model, reveals the outline of the salt edge. A second pass of reverse-time, prestack depth migration using full two-way wave equation was performed with an updated velocity model that consisted of the velocity gradient and salt dome. The second-pass migration brings out dipping sediments abutting the salt flank because these reflectors were illuminated by energy that bounced off the salt flank, forming prismatic reflections. In this target-oriented strategy, the computationally fast redatuming process eliminates the need for the traditional complex process of velocity estimation, model building, and iterative depth migration to remove effects of the salt canopy and surrounding overburden. This might allow this strategy to be used in the field in near real time.

Seismic interferometry and ambient noise tomography in the British Isles

“…Rickett and Claerbout, 1999;Lobkis and Weaver, 2001;Weaver and Lobkis, 2001;Campillo and Paul, 2003;Shapiro and Campillo, 2004;Sabra et al, 2005a,b;Shapiro et al, 2005;Yang et al, 2006;Draganov et al, 2006;Bensen et al, 2007Bensen et al, , 2008Zheng et al, 2008) and active or impulsive sources (e.g. Bakulin and Calvert, 2006;Slob et al, 2007;Lu et al, 2008;King et al, 2010), for computing or modelling synthetic waveforms (van-Manen et al, 2005(van-Manen et al, , 2006, and for noise prediction and removal from data Dong et al, 2006;Halliday et al, 2007Halliday et al, , 2010Curtis, 2008, 2009).…”

Interferometric correlogram‐space analysis

“…Intuitively, the process of stacking correlograms removes from them all correlated events except for stationary phase contributions (Snieder, 2004). The latter are produced by physical sources, whose rays pass through the virtual source and are received at the virtual receiver (Lu et al, 2008). Other parts of the cross-correlogram are conventionally regarded as noise, and as a result they are intended to be filtered out by the stacking operator.…”

Tutorial on seismic interferometry: Part 1 — Basic principles and applications

“…His work inspired many other researchers to develop interferometric methods for exploration geophysics. For example, VSP data can be transformed into crosswell data ͑Minato et al, 2007͒ or into single-well reflection profiles to improve salt-flank delineation and imaging ͑Willis et al, Xiao et al, 2006;Hornby and Yu, 2007;Lu et al, 2008͒. Interferometry can be used to turn multiples in VSP data into primaries and in this way enlarge the illuminated area ͑Yu and He et al, 2007;Jiang et al, 2007͒.…”